1. The Field of the Invention
"Wordprocessing" involves the use of a digital computer and a computer program running on the computer to manipulate printed characters in creating and editing printed documents. These documents can be displayed electronically on a computer display screen or printed on hardcopy. This document was created using a wordprocessing program ("wordprocessor"), WordPerfect 5.1. Manipulation of data in the form of printed characters is, indeed, a fundamental tool for human interaction with computers. Input devices such as keyboards provide the mechanism for feeding information to the computer, while output devices, such as video display terminals and printers, provide the mechanisms for viewing the results. Wordprocessors are a fundamental and vital tool of modern business.
Wordprocessors range in functionality from simple "text editors," which do no more than reproduce on the display screen the user's keyboard input, to sophisticated "desktop publishers," which enable the user to create, display, and print sophisticated, publication quality documents. Computer programs for wordprocessing have been in existence for many years. Only recently, however, have highly sophisticated wordprocessors become available for microcomputers such as IBM Personal Computers and compatible computers ("IBM PC's and compatibles").
Characters may be printed in various shapes and sizes. The appearance of characters on a printed page or display screen is referred to as its "font." Typically, a particular font consists of a character set of a distinct style containing the letters of the alphabet, numbers, and other frequently used symbols. A font is characterized by three elements: typeface (the style of the character, e.g., Times Roman or Courier), weight (e.g., bold or italic), and point size (the size of the font--one point being approximately 1/72"). Until recently, only a few standard fonts were available through wordprocessors running on microcomputers. Sophisticated, non-standard fonts typically had to be typeset by commercial printing organizations. In recent years, however, a large assortment of fonts have become available to microcomputer users through the use of wordprocessors.
Printers designed for use with microcomputers typically print characters in either of two modes: text or graphic. In order to print in text mode, a character must be pre-defined in the printer's memory. Thus, when printing in text mode, the printer receives data from the computer telling it what character to print and exactly where on the page to print it but not a definition of how to print it. The printer retrieves the definition of the character from its memory which then directs the printer's printing mechanism how to print the character. If that particular character is not defined in the printer's memory, however, it must be printed in graphics mode if it can be printed at all. In graphics mode, data is sent directly from the computer to the printer's printing mechanism telling it precisely how to print a character. Thus, the essential difference between text and graphics mode printing is the source of the data defining the character, with text mode data residing in the printer's memory and graphics mode data being supplied directly from the attached computer. Graphics mode printing obviously allows much greater flexibility in character style. It also can be much more time consuming due to the increased volume of data that must be sent from the computer to the printer.
Fonts that are printable in text mode are defined as either "hard fonts" or "soft fonts." Hard fonts consist of pre-defined font data that is stored in the printer's permanent, or "read only," memory ("ROM"), or on printer cartridges, which are data storage mechanisms that can be read directly by the printer. Soft fonts consist of data that is downloaded (transferred electronically) from the computer to the printer's temporary, or "random access," memory ("RAM") where it is stored until the printer is turned off or instructed to erase its memory. Most wordprocessors enable the user to print characters in text mode using either hard fonts or soft fonts. However, these wordprocessors are still limited in their font selection to fonts printable in text mode, i.e., hard fonts or soft fonts. The invention disclosed herein overcomes this limitation in font selection.
2. The Prior Art
In the early years of personal computing, only a small number of fonts were available for use with wordprocessors. Likewise, only a few types of printers were available for printing these fonts. Consequently, wordprocessing documents tended to be printer dependent in that they used a limited selection of fonts which were largely determined by the font capability of the attached printer. Today, however, hundreds of printers with diverse font printing capabilities are marketed for use with personal computers. Likewise, new fonts are increasingly available and easier to incorporate into wordprocessing documents. These new fonts may be utilized in varying combinations within wordprocessing documents. However, since a printer is capable of printing only a subset of all available fonts in text mode, if a document contains characters of a font that the printer is not capable of printing, they will not be printed.
The disclosed invention solves this problem, thereby allowing greater printer independence in wordprocessing documents. Specifically, many fonts which could not be used and printed in the same document prior to this invention can now be printed in the same document. Whereas the types of fonts that could be included in a document once were determined by the capability of the printer, the invention allows one to include a greater variety of fonts, including international and mathematical characters, independent of what the printer is capable of printing in text mode. Thus, a document may be created with multiple fonts and printed on different printers, regardless of whether each printer is capable of printing each font in the document in text mode.
Thus, the method and apparatus disclosed herein enable the user to print characters in both text mode and graphics mode from the same document in a manner that is transparent to the user, i.e., the user need not know which fonts require graphics mode and which do not. The invention enables such document to be printed using any printer that has a graphics mode, whether or not the printer is capable of printing the fonts in the document in text mode. Characters that cannot be printed in text mode will automatically be printed in graphics mode.